Slider Widget, Hero Widget and Layout Slider Widget don’t show Parallax option

Hello to all,
I started to use SiteOrigin plugin right now, I’m following the online guides to better understand the product and almost anything is going well.
Just a moment ago I tried to use a parallax for a background image, but without success.
I’ve followed the instructions of the below link:

https://siteorigin.com/premium-documentation/plugin-addons/parallax-sliders/

When I click on the drop-down menu “Background image type” I should see the option “Parallax” on all the three kind of widgets. Unfortunately, I don’t see this option (I see only “Cover” or “Tile”)…what’s the reason? Am I doing something wrong or what else?
Thanks for your kind support.